Effect of Organic Matter Application on Methane Emission from Some Japanese Paddy Fields

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Emission rates of CH_4 from four Japanese paddy fields were measured throughout the cultivation period in 1988 by using the closed chamber method. Large seasonal variations of the CH_4 flux were observed. The emission was closely related to the decrease of the redox potential (Eh) in paddy soils. Drainage and supplementary application of mineral fertilizer substantially reduced the CH_4 emission. Emission rates of CH_4 differed markedly with the soil types. The highest rate was observed in a paddy field consisting of Peat soil (44.8 g-CH_4/m^2 during a cultivation period), followed by Gley soil (8.0-27.0). The emission rates in the Andosols were significantly lower (0.6-12.6). Application of rice straw at a rate of 6-9 t/ha to the paddy fields increased the CH_4 emission rates 1.8- to 3.5-fold. Application of compost slightly increased the CH_4 emission. Annual emission rates of CH_4 from individual plots where positively correlated with the contents of readily mineralizable carbon (RMC) in paddy soils collected before flooding, suggesting that RMC is one of the main factors affecting CH_4 emission from flooded soils.
社団法人日本土壌肥料学会の論文